Plasma arc torches are widely used in the cutting and marking of materials. A plasma torch generally includes an electrode and a nozzle having a central exit orifice mounted within a torch body, electrical connections, passages for cooling, and passages for arc control fluids (e.g., plasma gas). Optionally, a swirl ring is employed to control fluid flow patterns in the plasma chamber formed between the electrode and nozzle. In some torches, a retaining cap can be used to maintain the nozzle and/or swirl ring in the plasma arc torch. The torch produces a plasma arc, a constricted ionized jet of a gas with high temperature and high momentum. Gases used in the torch can be non-reactive (e.g., argon or nitrogen) or reactive (e.g., oxygen or air). In operation, a pilot arc is first generated between the electrode (cathode) and the nozzle (anode). Generation of the pilot arc can be by means of a high frequency, high voltage signal coupled to a DC power supply and the torch or by means of any of a variety of contact starting methods.
One category of handheld plasma arc torch systems includes a manual gas control knob on the control panel of the power supply or power supply housing. Before cutting a workpiece, an operator is required to manually adjust the gas pressure or gas flow rate based on the process parameters set forth in a cut chart. The operator manually adjusts the gas pressure or flow rate for each type of cut and therefore constantly refers to the cut chart for the appropriate gas pressure or flow rate. Moreover, if the operator inadvertently inputs an incorrect gas pressure or flow rate, the plasma arc torch can operate incorrectly or inefficiently.
Another category of handheld systems eliminates the gas control by automatically setting the gas pressure based on the user-selected current level and mode (i.e., gouging or cutting). This category of handheld plasma arc torches does not provide the operator with any flexibility in setting the gas pressure beyond the preset automated systems. Therefore, if the operator determines that the gas pressure or flow rate should be changed due to a changed operating parameter or to optimize the plasma arc torch, the operator does not have the flexibility to make these operational and/or optimizing adjustments.